Request combining in multiprocessors with arbitrary interconnection networks

Abstract

Several techniques have been proposed to allow parallel access to a shared memory location by combining requests. They have one or more of the following attributes: requirements for a priori knowledge of the request to combine, restrictions on the routing of messages in the network, or the use of sophisticated interconnection network nodes. We present a new method of combining requests that does not have the above requirements. We obtain this new method for request combining by developing a classification scheme for the existing methods of request combining. This classification scheme is facilitated by separating the request combining process into a two part operation: determining the combining set, which is the set of requests that participate in a combined access; and distributing the results of the combined access to the members of the combining set. The classification of combining strategies is based upon which system component, processor elements, or interconnection network performs each of these tasks. Our approach, which uses the interconnection network to establish the combining set and the processor elements to distribute the results, lies in an unexplored area of the design space. We also present simulation results to assess the benefits of the proposed approach. >